Durability of Zirconium‐Containing Ceramic Waste Forms in Water

Abstract

The durability of three ceramic waste forms containing Zr as a constituent is examined at 90" and 150°C in HCl or deionized water. The three ceramic waste forms examined are: (A) 10-moI%-YZO3-stabilized ZrOZ, (B) La2ZrZ07 with a pyrochlore structure, and (C) CaZr03 with a perovskite structure. Each form contains an appropriate amount of Ce, Nd, and Sr to simulate the leaching behavior of actinides, lanthanides, and alkaline-earth fission products from highlevel nuclear waste. Two forms, (A) 10-mol%-YZ03-stabilized ZrOz and (B) LazZrZ07 with a pyrochlore structure, show excellent durability in HCI and deionized water. For example, leach rates of all constituents in the LaZZrZO7 waste form are less than about g.m-'.d-' at 150°C for a leach time of 32 d in deionized water. [

Phase evolution and chemical durability of co-doped Gd2Zr2O7 ceramics for nuclear waste forms

“…Since the released actinides can form dissolved or colloidal radionuclide complexes by contacting and reacting with water, and it might finally extend to the biosphere by transportation with underground water flow [20,21]. Furthermore, the prevention of water ingression to the nuclear waste is extremely difficult, which may form water soluble salt and increase the leachability of certain species [22]. Thus, it is necessary to assess the chemical durability of Gd 2 Zr 2 O 7 for the final security.…”

Dissolution of ZrO2 based pyrochlores in the acid pH range: A macroscopic and electron microscopy study

“…Therefore, the Arrhenius approach may not be appropriate for the prediction of the dissolution rate as a function of temperature in this type of system. Kamizono et al (1991) reported dissolution rates of La-Zrbased pyrochlores obtained in deionised water in the temperature range between 90°C and 150°C. From their data, a similar temperature dependency as for the pyrochlore in this study can be derived.…”

“…In the literature mainly static dissolution studies exist for ZrO 2 based pyrochlores (Hayakawa and Kamizono, 1993a,b;Kamizono et al, 1991).…”

Fundamental and Technological Aspects of Actinide Oxide Pyrochlores: Relevance For Immobilization Matrices

“…Regarding the durability of the pyrochlore oxides, studies on the La-zirconate (La 2 Zr 2 O 7 ) pyrochlore oxide suggest a particularly low leachability in aqueous systems [9]. Additional work with simulated high level nuclear waste materials (Ce 4 " Nd", Sr", etc.)…”